Handheld wireless devices are essentially hand held radios that communicate by exchanging radio frequency signals with network access points using predefined signaling protocols. Each handheld device may include multiple interfaces for communicating using a variety of different wireless networks. A typical handheld wireless device is a mobile phone which includes a cellular interface that allows the phone to connect to a Public Switched Telephone Network (PSTN) via a cellular network such as a Global System for Mobile Communications (GSM) network. A handheld device may also include interfaces that allow the device to communicate using General Packet Radio Service (GPRS) protocols in a GPRS network, Wi-Fi (IEEE 802.11) protocols in a Wi-Fi network, WiMAX (IEEE 802.16) protocols in a WiMAX network or Bluetooth protocols for Bluetooth exchanges. The different wireless networks (Wi-Fi, WiMAX, etc.) are interconnected via gateways, where a gateway is a node on a network that serves as an entrance to another network. Wireless access points or base stations transmit radio frequency signals to indicate the existence of a wireless network to a wireless device. A wireless device will associate (or connect) with one of the wireless access points or base stations at a network point of access to gain access to the wireless network. Once the wireless device has made a connection to a wireless network, the wireless device may access resources in the wireless network, as well as resources in networks connected to the wireless network via gateways.
Radio frequency signals, however, have a limited transmission range and when a mobile device moves it may move out of range of the access point or base station that connects it to the desired resource. In order to maintain resource access, the mobile device must connect to another access point or base station. The access point or base station may be part of administrative domain associated with the prior network or may be a network associated with a different administrative domain.
Many enterprise networks are protected from unauthorized access using various Network Access Control (NAC) mechanisms, such as 802.1x and security mechanisms such as Virtual Private Networks (VPNs), keying mechanisms and the like. For example, within certain enterprise domains the wireless data network is protected by an IPSEC VPN gateway. Some access points are protected with different standard security mechanisms, such as WEP, WEP2, 802.1x, etc.
In order to gain access to such networks, users must have prior knowledge of the type of security mechanism used by the network. Security mechanisms may be found at multiple layers of then network stack. For example, layer two may have an 802.11 security mechanism, layer 3 may have an IPSEC mechanism, layer 7 may have a user authentication mechanism, etc. Information regarding the particular security mechanisms used at each network layer is frequently provided in text form or as a downloadable client to the authorized users by a network administrator when the mobile device is initially delivered to the authorized users.
Because security mechanisms differ between networks, mobile users who transition between networks may have their communication interrupted as they transition between secured networks. As a network device attempts to connect to a new network, it initiates connections using various, known security mechanisms one by one until the correct security mechanism is, by chance, detected and the connection is allowed. It would be desirable to increase convergence time by reducing delays associated transitions between secure networks.